A Comparative Study of Linear, Random Forest and AdaBoost Regressions for Modeling Non-Traditional Machining

Non-traditional machining (NTM) has gained significant attention in the last decade due to its ability to machine conventionally hard-to-machine materials. However, NTMs suffer from several disadvantages such as higher initial cost, lower material removal rate, more power consumption, etc. NTMs involve several process parameters, the appropriate tweaking of which is necessary to obtain economical and suitable results. However, the costly and time-consuming nature of the NTMs makes it a tedious and expensive task to manually investigate the appropriate process parameters. The NTM process parameters and responses are often not linearly related and thus, conventional statistical tools might not be enough to derive functional knowledge. Thus, in this paper, three popular machine learning (ML) methods (viz. linear regression, random forest regression and AdaBoost regression) are employed to develop predictive models for NTM processes. By considering two high-fidelity datasets from the literature on electro-discharge machining and wire electro-discharge machining, case studies are shown in the paper for the effectiveness of the ML methods. Linear regression is observed to be insufficient in accurately mapping the complex relationship between the process parameters and responses. Both random forest regression and AdaBoost regression are found to be suitable for predictive modelling of NTMs. However, AdaBoost regression is recommended as it is found to be insensitive to the number of regressors and thus is more readily deployable.

An Integrative Experimental Approach to Design Optimization and Removal Strategies of Supporting Structures Used during L-PBF of SS316L Aortic Stents

One of the fundamental challenges in L-PBF of filigree geometries, such as aortic stents used in biomedical applications, is the requirement for a robust yet easily removable support structure that allows each component to be successfully fabricated without distortion. To solve this challenge, an integrative experimental approach was attempted in the present study by identifying an optimal support structure design and an optimized support removal strategy for this design. The specimens were manufactured using four different support structure designs based on the geometry exposed to the laser beam during the L-PBF. Support removal procedures included sand blasting (SB), glass bead blasting (GB), and electrochemical polishing (ECP). The two best-performing designs (line and cross) were chosen due to shorter lead times and lower material consumption. As an additional factor that indicates a stable design, the breaking load requirement to remove the support structures was determined. A modified line support with a 145° included angle was shown to be the best support structure design in terms of breaking load, material consumption, and manufacturing time. All three procedures were used to ensure residue-free support removal for this modified line support design, with ECP proving to be the most effective.

Psychological and Social Factors Associated with Coexisting Frailty and Cognitive Impairment: A Systematic Review

Those living with coexistent frailty and cognitive impairment are at risk of poorer health outcomes. Research often focuses on identifying biological factors. This review sought to identify the association psychological and social factors have with coexisting physical and cognitive decline. Six databases were systematically searched in July 2020. Studies included individuals aged 60 years or older identified as being both frail and cognitively impaired. A narrative synthesis examined patterns within the data. Nine studies were included, most employed a cross-sectional design. Depression was investigated by all nine studies, those with coexistent frailty and cognitive impairment had higher levels of depressive symptoms than peers. Findings were mixed on social factors, although broadly indicate lower education, living alone and lower material wealth were more frequent in those living with coexistent decline. Further research is needed to explore potentially modifiable psychological and social factors which could lead to the development of supportive interventions.

Investigation of the formability behaviour of optimized tufted and un-tufted multi-layer carbon preforms during the stamping process

The originality of this work consists of studying the stamping behaviour of tufted and un-tufted multi-layer carbon preforms. Several tufted preforms with different stratifications have been manufactured. The stamping test was carried out using a hemispherical punch and conducted at two blank-holder pressures (0.05 and 0.2 MPa). The experimental data show that the addition of tufting yarn, the number of layers and the blank-holder pressure significantly affected the forming behaviour: the tufted preform presents a higher punch force, lower material drawin and shear angles with significant structural defects than the un-tufted preform. The increase of the blank-holder pressure increases all these characteristics and emphasizes the structural defects on the fibrous reinforcements. Similarly, the transition from two layers to four layers lamination at the same blank-holder pressure is followed by an increase of the punch force, reducing the material draw-in and the shear angles especially those measured at the transient zone, and causes more structural defects on all stamped preforms. Therefore, two localized tufting configurations, Right Localized Tufted and Inclined Localized Tufted, at the stamping transition area have been proposed. The results show that these two configurations present a minimum punch force and a maximum material draw-in similar to those measured on the un-tufted structure. The shear angles are much greater than those recorded on the conventionally (fully) tufted preform. Thus, the localized tufting in the most stressed areas proves to be the most suitable solution for the stamped preforms.

Intrinsic differences and realistic perspectives of lithium-sulfur and magnesium-sulfur batteries

Following in the footsteps of lithium-sulfur batteries, magnesium-sulfur batteries offer a high theoretical energy content and are composed of cheap and more environmentally-friendly electrode materials. In comparison to lithium-sulfur, however, current magnesium-sulfur batteries suffer from higher overpotentials at the magnesium anode and the sulfur cathode, lower material utilization and reversibility at the sulfur cathode, and an excessive demand of electrolyte. Here, a side-by-side comparison of the processes at the two metal anodes and at the sulfur cathode in Li+- or Mg2+-based electrolytes highlights how most of the challenges facing magnesium-sulfur batteries are intrinsically rooted in the nature of the magnesium species, requiring different research directions than lithium-sulfur batteries. An evaluation of the energy content and the corresponding costs on a practical cell stack level illustrates the importance of overcoming these challenges.

RESEARCH OF MATERIALS PROPERTIES FOR 3D PRINTING OF ORTHOSES

In this paper examines the possibilities of applying 3D printing in the manufacture of orthoses. Features of 3D printing of biocompatible materials are analyzed. In this work, mechanical bending tests of three printed samples were performed. Based on test results, PETG material is selected for 3D modeling and printing. Technological properties of 3D printing were summarized. Modeling and printing of the orthoses prototype, compared to traditional methods, takes less time, and uses lower material costs, does not require much physical effort, is well suited to the patient’s body anatomy, and has a variety of design options.

Intermetallics Disappearance Rate Analysis in Double Multiphase Systems

Electric corrosion of aluminium and copper is investigated experimentally. It is found that the electric corrosion of copper is higher than the electric corrosion of aluminium. It is also clarified that the intrinsic diffusion coefficient of Cu is higher than the intrinsic diffusion coefficient of Al in each phase, so inert markers move to Cu. Copper has a higher electric conductivity, higher thermal conduction, and lower material cost than gold, so it is possible to use Cu instead of Au for wire bonding in microelectronics packaging, because the thin Al pad (1.2 μm thickness) can prevent gold and copper corrosion. Intermetallics disappearance and Kirkendall shift rates calculation methods are proposed. Methods involve mass conservation law and concentration profiles change during mutual diffusion. Intermetallics disappearance and Kirkendall shift rates in Al-Cu (Al is thin layer on Cu), Cu-Al (Cu is thin layer on Al), Al-Au, Zn-Cu, and Cu-Sn systems are analyzed theoretically using literature experimental data. Diffusion activation energies and pre-exponential coefficients for Cu-Sn system were calculated combining literature experimental results.

Analysis of bench testing results and evaluation of economic effect due to introduction of combine harvester cleaning improvement solutions

One of the possible ways to increase the efficiency of cleaning separation could be the grain fortification of the heap feeding to chaffer sieve and intensification of grain sifting through this sieve. This direction makes it possible to develop the air-sieve cleaning with the pneumatic and inertia separator for high-producing combine harvester. Cleaning improvement will provide agricultural production with the equipment with higher agrotechnical capabilities and lower material expenses.

JUSTIFICATION OF PARAMETERS FOR IMPROVING THE FLOW REGULATOR OF SPRINKLERS OF THE KUBAN – LK1 MACHINE»

Проблема и цель. В статье отмечается сложность работы дождевальной машины (ДМ) «КубаньЛК1» на склоновых землях, определяемых перепадом геодезических высот, вызывающих переполив, особенно в концевой части. Это приводит к нарушению технологического процесса полива из-за снижения тягово-сцепных характеристик последних тележек ДМ, что и послужило целью данного исследования. Методология. Для достижения цели исследования и ответа на поставленные вопросы было проанализировано обеспечение автоматизированной групповой работы машин с дистанционным управлением, возможность реверсивного движения с поливом и без подачи воды в машину, проходимость на полях с низкой несущей способностью почв. Обосновывается возможность стабилизации расхода в концевой части ДМ дождевальных аппаратов в пределах 1,8-2,0 л/с при установке мембранного регулятора расхода типа Valtec VT.085 (масса ≈ 19,0 H). При оснащении в указанной части трубопровода регулирующими устройствами большего количества аппаратов (десять и более) материалоемкость в разы возрастет. Приводится расчет по обоснованию соответствующих размеров регулятора с проведением поисковых исследований по их уточнению. Результаты. Результаты настоящего исследования показали, что для снижения весовых характеристик регулирующего устройства на 50-60 % должна быть задача замены его на более легкую, усовершенствованную, малорасходную модификацию. Заключение. Отмечается, что проведенные теоретико-поисковые исследования позволили установить: наиболее приемлемым для регулирования расхода в концевой части дождевальной машины «Кубань-ЛК1» может быть усовершенствованное регулирующее устройство мембранного типа; обоснованность этого определяется большей точностью процесса регулирования (93-95 %) и меньшей материалоемкостью по сравнению с серийными моделями регуляторов (на 50-60 %) Problem and purpose. The article notes the complexity of the operation of the Kuban-LK1 sprinkler on sloping lands determined by the diference in geodetic heights that cause excess watering, especially in the end part. This causes some violation of the irrigation process due to a decrease in the traction characteristics of the last DM trolleys, which is the purpose of this study. Methodology. To achieve the research purpose and answer the research questions, the provision of automated group operation of remote-controlled machines was analyzed, as well as the possibility of reverse movement with irrigation and without water supply to the machine, and cross-country ability in felds with low soil bearing capacity. The possibility of stabilizing the fow rate in the end part of the DM sprinklers in the range of 1.8- 2.0 l/s when installing a Valtec VT.085 type diaphragm fow controller (weight ≈ 19.0 H) was justifed. If more devices (ten or more) were equipped with regulating devices in the specifed part of the pipeline, the material consumption would increase signifcantly. A calculation was given to justify the appropriate size of the regulator with search studies to refne them. Results. The results of this study showed that in order to reduce the weight characteristics of the control device by 50-60 %, the task is to replace it with a lighter, improved, low-cost modifcation. Conclusion. It is noted that the conducted theoretical and search studies have allowed to establish that an improved membrane-type regulating device can be the most acceptable for regulating the fow rate in the end part of the Kuban-LK1 sprinkler. Its validity is determined by the greater accuracy of the control process (93-95 %) and lower material consumption compared to serial models of regulators (50-60 %).

Limit state of hull grillages made of polymeric composites

This paper presents the results of limit-state research for polymeric-composite grillages of hull under bending. Taking geometric non-linearity into account, it was possible to estimate supercritical straining of structural members and global buckling effect of certain beams upon overall hull stiffness. Numerical studies have shown that with given thicknesses and dimensions of principal members strength margin in terms of design bending moment is not less than 5, which means that these structural members could be further optimized towards lower material consumption.